Introduction: Kasese District is prone to cholera outbreaks and this was its third outbreak in 15 years. In May 2015, Kasese District reported a cholera outbreak that had lasted 3 months and caused >100 infections. A team from Ministry of Health set out to support the local response team in identifying the mode of transmission and informing control measures.Methods: we defined a suspected case as onset of acute watery diarrhoea from 1st February 2015 onward; a confirmed case was a suspect case with Vibrio cholerae cultured from a stool sample. We reviewed medical records for case finding and conducted a case-control study to compare the exposures of 49 confirmed cases with those of 201 asymptomatic controls, matched by village and age group. We conducted environmental assessments and tested water samples for faecal contamination.Results: we identified 183 suspected cases including 61 confirmed cases (serotype inaba) and 2 deaths from February to July. The outbreak occurred in 80 villages and affected all age groups; the highest attack rate occurred in persons aged 5-14 years (4.1/10,000). Stratified epidemic curves showed that the outbreak started in Bwera Sub-county bordering the Democratic Republic of Congo, and spread eastward. 94% (46/49) of cases compared with 75% (152/201) of controls drank water without boiling or treatment (ORM-H = 5.9; 95%CI = 1.6-22). The main water sources, public piped water (consumed by 39% of cases and 38% of controls) and stream water (consumed by 29% of cases and 24% controls), both had high levels of E. coli, a marker of faecal contamination. Environmental assessment revealed evidence of open defaecation along the streams. No food items were significantly associated with illness.Conclusion: drinking unsafe water contaminated by feces caused this outbreak. We recommended rigorous disposal of patients’ feces, chlorination of piped water, and drinking boiled or treated water. The outbreak stopped 6 weeks after initiating implementation of these control measures.

Introduction: Kasese District is prone to cholera outbreaks and this was its third outbreak in 15 years. In May 2015, Kasese District reported a cholera outbreak that had lasted 3 months and caused >100 infections. A team from Ministry of Health set out to support the local response team in identifying the mode of transmission and informing control measures.Methods: we defined a suspected case as onset of acute watery diarrhoea from 1st February 2015 onward; a confirmed case was a suspect case with Vibrio cholerae cultured from a stool sample. We reviewed medical records for case finding and conducted a case-control study to compare the exposures of 49 confirmed cases with those of 201 asymptomatic controls, matched by village and age group. We conducted environmental assessments and tested water samples for faecal contamination.Results: we identified 183 suspected cases including 61 confirmed cases (serotype inaba) and 2 deaths from February to July. The outbreak occurred in 80 villages and affected all age groups; the highest attack rate occurred in persons aged 5-14 years (4.1/10,000). Stratified epidemic curves showed that the outbreak started in Bwera Sub-county bordering the Democratic Republic of Congo, and spread eastward. 94% (46/49) of cases compared with 75% (152/201) of controls drank water without boiling or treatment (ORM-H = 5.9; 95%CI = 1.6-22). The main water sources, public piped water (consumed by 39% of cases and 38% of controls) and stream water (consumed by 29% of cases and 24% controls), both had high levels of E. coli, a marker of faecal contamination. Environmental assessment revealed evidence of open defaecation along the streams. No food items were significantly associated with illness.Conclusion: drinking unsafe water contaminated by feces caused this outbreak. We recommended rigorous disposal of patients’ feces, chlorination of piped water, and drinking boiled or treated water. The outbreak stopped 6 weeks after initiating implementation of these control measures.